1. Field of the Invention
This invention relates to a crystalline inorganic material containing cobalt, boron and oxygen having a specified X-ray pattern. This invention also relates to a solid inorganic material containing cobalt, boron, oxygen and, optionally, aluminum made by combining sources of cobalt (II) ions, boria and, optionally, alumina in aqueous media within a controlled pH range under autogenous conditions at elevated temperature, and the use of such material in catalytic compositions for the conversion of organic compounds. More particularly, this invention relates to a solid inorganic material containing cobalt, boron and oxygen made by combining sources of cobalt (II) ions and boria in aqueous media within a controlled pH range under autogeneous conditions at elevated temperature, and the use of such solid in catalytic compositions for the conversion of organic compounds, particularly the oxidation and oxidative dehydrogenation of hydrocarbons.
This invention also relates generally to a method for partially oxidizing one or more oxidizable substituents on an aromatic compound and more particularly concerns performance of the aforesaid partial oxidation with the aromatic compound in the liquid phase and in the presence of a solid heterogeneous catalyst to form a partially oxidized aromatic product.
2. Description of the Prior Art
The use of cobalt in catalysts, particularly in the petroleum and petrochemical industries, is well known. Catalysts containing cobalt have been used in the petroleum industry for hydrodesulfurization, hydrodenitrification, and reforming. In the synthetic fuels area, cobaltcontaining catalysts have been used to liquify coal and to upgrade coal, tar sands and shale liquids. The have also been employed as Fischer-Tropsch catalysts. The use of cobalt-containing solids as catalysts is also to be found in the petrochemical industry where they have been used as hydroformylation and polymerization catalysts. Most of these uses in both the petroleum and petrochemical industries employ cobalt-containing catalysts in heterogeneously catalyzed processes. However, these heterogeneous cobalt-containing catalysts are not useful as alkylaromatic oxidation catalysts. An example of the use of a cobalt-containing catalysts system in homogeneous catalysis is in the production of terephthalic acid where paraxylene is oxidized in a liquid-phase process in the presence of oxygen to the aromatic dicarboxylic acid.
In the area of the oxidation of organic materials, both liquid-phase and vapor-phase processes are known For example, phthalic anhydride is made commercially by the vapor-phase oxidation of orthoxylene over a vanadium catalyst and, as described above, terephthalic acid is made by liquid-phase oxidation of terephthalic acid using a cobalt and manganese combination promoted by bromine in acetic acid. Many commercial advantages could result if a stable and active heterogeneous oxidation catalyst could be found for the liquid-phase oxidation of organic compounds, and the importance of such a catalyst would be enhanced if it could also show utility for vapor-phase oxidations.
The published literature also describes a few borate hydroxides. For example, the structures of the minerals szaibelyite, Mg(BO.sub.2)OH, and sussexite, Mn(BO.sub.2)OH, and mixed Mg/Mn analogues have been published. See J. Mineral, 2,78 (1957). A copper analogue has also been reported. The magnesium compound is described in U.S. Pat. No. 4,160,705 as a coating on electrical steel, and the coating is said to be prepared by electrolytic deposition.
Now it has been found that solid compositions containing cobalt (II), boria, optionally alumina, and oxygen are useful as an oxidation catalyst in a heterogeneously catalyzed liquid-phase process, and that the same compositions also exhibit utility for gas-phase oxidation reactions.
It is well known that aromatic hydrocarbons having at least one oxidizabe substituent group can be converted into carboxylic acid products by effecting oxidation of such groups under controlled conditions. Such conditions have generally included the use of a known oxidation catalyst together with a suitable solvent such as a low molecular weight aliphatic carboxylic acid, such as acetic acid. A typical catalyst system comprises compounds of manganese and/or cobalt, together with a bromine-affording material. U.S. Pat. No. 3,092,658 describes the use of such a process for the continuous oxidation of substituted aromatic hydrocarbons to their corresponding carboxylic acid derivatives, particularly for the preparation of the isomeric phthalic acids from their xylene precursors in an acetic acid solvent.
Such liquid phase oxidation of the oxidizable substituents of an aforesaid aromatic compound to an aromatic carboxylic acid is a highly exothermic chemical reaction. Volatilizable acidic solvents, such as acetic acid, are used both to solubilize the reaction mixture and to dissipate the heat given off by this exothermic reaction. Conventionally, the oxidation in the liquid phase of the oxidizable substituents in the aromatic compound to form aromatic carboxylic acids is generally performed in a vented, well-mixed oxidation reactor, with a substantial portion of the heat generated by the exothermic oxidation reaction being removed by vaporizing directly from the reaction mixture a portion of the solvent and aromatic compound contained within the reactor.
The materials vaporized as a result of the heat generated in the exothermic reaction, together with unreacted oxygen, pass upwardly through the reactor and are withdrawn from the reactor at a point above the reaction mixture liquid level for the reactor. The vapors are passed upwardly and out of the reactor to an overhead reflux condenser system where the vaporized solvent, water and unreacted aforesaid aromatic compound are condensed. The resultant condensate is thereafter separated, e.g., in a reflux splitter, into a portion having a relatively higher water concentration and a portion having a relatively lower water concentration. The separated portion having a relatively lower water concentration, now at a temperature less than the reactor contents' temperature, is refluxed back into the reactor by gravity. Conventionally, the refluxed portion of the condensate is returned directly to the reactor through a process line external to the reactor. The noncondensable gases, carried along with the vaporized reactor material, are vented.
In such an oxidation system the procedures used to recover and dehydrate the solvent are elaborate and expensive and a significant loss of the solvent, typically acetic acid, occurs, and the loss is attributable to oxidation, handling losses, volatility, and the like. In order to avoid this economic penality, attempts have been made to operate without a solvent but without significant success. A more promising approach has involved the use of a solvent system comprising water or some other convenient solvent. However, many of the aforesaid aromatic compounds having oxidizable substituents are only weakly soluble in water or in some of the other likely solvents. Consequently, it is highly desirable to convert in a first stage--for example, by partial oxidation--the aforesaid substituent aromatic compounds to materials that are soluble in water or some other convenient solvent and to do so by a process that permits such materials to be recovered in a highly pure form without the use of costly or elaborate catalyst or solvent separation or treatment procedures. The resulting materials would then be completely oxidized in a second stage in water or some other convenient solvent. Furthermore, even if a low molecular weight carboxylic acid such as acetic acid were employed as the solvent in a second oxidation stage in a multistage oxidation system, it would be highly desirable to employ a first oxidation stage that affords an oxidation product therefrom that also can be recovered in a highly pure form without the use of costly or elaborate catalyst or solvent separation or treatment procedures in the first oxidation stage.